1. Field of Invention
The present invention relates to a petroleum extraction machinery equipment, and more particularly to a top-mounted digital-control tower pumping unit.
2. Description of Related Arts
Currently, various petroleum extraction machinery equipments are used in the petroleum production. Among those the beam pumping unit is the most mature one although it is being gradually replaced by the tower type pumping unit due to the disadvantages of its gigantic and heavy structure, high energy consumption, low efficiency, and inconvenient maintenance and adjustment. The existing tower pumping units mostly employ the reducer box to decelerate in which the motor is connected with the reducer via the coupling. The large gear, the head sheave and the hoisting wheel are fastened together and are seated on the head sheave shaft via the bearing. The head sheave is clamped tightly by the head sheave fastening device. During the oil pumping, the motor drives the reducer box through the coupling, the small gear connected with the output shaft of the reducer box is engaged with the large gear, so that the head sheave fastened to the large gear regularly rotates in the forward and backward directions, thereby driving the polish rod to move upwards and downwards. In these tower pumping units, the transmission gear mechanism of the reducer box is difficult and expensive to produce. Furthermore, the big noise is caused by the gear meshing during operation, and the frequent maintenances are needed due to the always occurred oil leakage. Also, there exists a pumping unit using the direct motor drive without reducer box. This kind of pumping unit overcomes the disadvantages of the reducer box with a one stage belt type speed reduction or without the reducer box. However, the direct motor drive mechanism increases the cost about 5 to 10 times compared with the beam pumping unit. Simultaneously, using the one-stage belt type speed reduction results in the disadvantages of deficient power and short life of the belt. Therefore, it is necessary to develop a new pumping unit to overcome the shortcomings mentioned above.